This invention relates to automotive braking systems in general, and more particularly relates to a method and apparatus for the anti-locking braking of an automotive vehicle, particularly a motorcycle.
The Federal Republic of Germany Pat. No. 31 19 144 discloses an anti-locking braking system that includes an electronic section which recognizes overbraking of the wheel upon circumferential deceleration reaching 12 m/s.sup.2 and, by means of a hydraulically controlled pressure modulator, interrupts the connection between an operator actuated master cylinder and the wheel cylinder to reduce braking pressure acting on the wheel cylinder. Braking pressure is then reduced by increasing the volume in a chamber of the pressure modulator until a lower circumferential deceleration threshold of 10 m/s.sup.2 is reached, whereupon an exactly defined further reduction of the braking force takes place in an amount calculated from the moment of inertia of the rotating wheel, which leads to a reduced deceleration of the braked wheel. This is followed by a reduction in volume of the chamber resulting in increasing brake pressure so that circumferential deceleration of the wheel rises and upon reaching 12 m/s.sup.2 again, a new control cycle commences.
The change in volume of the pressure modulator chamber is effected by a stepped piston which is arranged in the modulator to form equalization and working chambers which are separated from each other. The equalization chamber is connected to the brake cylinder and the working chamber is connected to the brake cylinder by a servo valve, a hydraulic circuit which is formed of a motor-driven pump with non-return valve behind it, and a pressure accumulator connected in parallel therewith.
Upon over-braking of the wheel, the servo valve is so displaced that pressure built up in the working chamber of the pressure modulator pushes the stepped piston toward a lower dead center position, as a result of which the equalization chamber is enlarged and the active brake pressure in the wheel cylinder is reduced. For increasing the braking force, the servo valve switches in such a manner that hydraulic fluid can flow from the working chamber into the tank, while the stepped piston is pushed by spring force toward an upper dead center.
An anti-locking device which operates in accordance with this method was developed for use in two-track (at least four wheels) vehicles and cannot be integrated practically in motorcycles since the hydraulic circuit with its numerous parts requires a large amount of space and because handling properties would be negatively influenced by the necessarily increased weight of the vehicle.